Vascular atherosclerotic lesions that create arterial luminal narrowing are typically treated in angioplasty procedures via catheters provided with an inflatable balloon. The catheter is advanced, typically following a guidewire, to an opening within the atherosclerotic lesion of the narrowed artery. Once the inflatable balloon has been arranged at the artery narrowing, it may be inflated and deflated, sometimes repeatedly. The inflation, with successive deflation, of the inflatable balloon within the artery can reduce the extent of the arterial luminal narrowing, and restore a suitable blood flow.
In many cases, patients develop a re-narrowing of the vessel lumen at the intervention point within a few months. Such re-narrowing, or restenosis, is due to a cell hyperproliferation process, particularly of the vascular smooth muscle cells, and may be due to the dilating action caused by the inflatable balloon.
Inflatable balloons or stents can be coated with a drug having anti-proliferative action to prevent or retard restenosis. Among the drugs usually employed to such aim, paclitaxel (taxol) has proved to be particularly efficient.
However, with current therapies the paclitaxel delivered by the balloon catheter to the wall of the vessel drops below an effective concentration after a period of time. For example, the paclitaxel may be present on the vessel wall in an effective anti-proliferative concentration for about 6 months following treatment. It may be desirable to increase the amount of time that paclitaxel is present at the vessel wall in an effective concentration.